1. Field of the Invention
This invention relates generally to systems and methods for positioning and, more particularly, to systems and methods of positioning a transducer in a storage device such as a tape drive.
2. Description of Related Art
The 3584 LTO drive head is positioned based on the bottom position as a reference position and moves to a specified position with a stepping motor. The position of the head is unknown when the drive is switched on. Then, the bottom position is sought while the head is moved. The head is sometimes moved out of the permissible range during the search, which may break the head mechanism.
Specifically, the conventional 3854 LTO drive has a light blocking shield, attached to the head, for detecting the bottom position and a photo-interrupter attached to a case. The bottom position is based on the border between the place where the photo-interrupter crosses the light-blocking shield and the place where the photo-interrupter does not cross the light-blocking shield. If the photo-interrupter crosses the light-blocking shield when the drive is switched on, the border can be found while the head is moved in the direction away from the bottom. If the photo-interrupter does not cross the light-blocking shield, the border can be found while the head is moved toward the bottom. If the sensor is unplugged, the drive is always in the same situation as when the photo-interrupter crosses the light-blocking shield. Accordingly, in such a case, the method causes the head to keep moving in the direction away from the bottom even over the range allowed for the head to move, which breaks the head mechanism.
The 3584 Gen4 drive has a mechanism for checking whether the photoreceptor side of the photo-interrupter responds or not by controlling ON/OFF of the LED of the photo-interrupter for the purpose of checking the operation of the photo-interrupter. That can confirm that the drive is plugged. If no response is detected, the mechanism cannot determine whether the drive is unplugged or the photo-interrupter is crossing the light-blocking shield. Then, the mechanism slightly moves the head. If the head is already at the limit of the range allowed for it to move, that movement breaks the head. (When the drive is powered down, the head is usually placed at a place other than the bottom position to prevent that incident. Sometimes, however, the power abruptly breaks when the head is at the bottom position.)
Mechanically, that incident can be prevented by removing the ditch of screws for the head not to move to out of the range. For that purpose, the length of the ditch to be removed needs to be wide enough for the size of the head. This is not the best measure when the height of the device is limited.
The head may be physically stopped by an overshoot preventing piece (Japanese Unexamined Patent Application Publication No. 5-128701, Japanese Unexamined Patent Application Publication No. 10-334536.)